1. Field of the Invention
The present invention relates in general to a method and apparatus for forming envelopes. In particular, the present invention relates to an improved method and apparatus for forming clasp envelopes, including an improved apparatus for attaching the clasp to the envelope.
2. Description of the Related Art
Clasp envelopes have been known for a number of years. Such envelopes are typically formed of paper folded to form front and back panels joined about three sides to define a pouch therebetween. The fourth side typically includes an openable flap to close the aperture of such pouch. The flap includes a hole, which, when the flap is in the closed position, registers with a metallic clasp fixed to the back panel of the envelope and having two projections extending in opposite directions. These projections may be bent upwardly to be received through the hole in the flap and then bent back to their original flat position to engage the upper surface of the flap to thereby retain the flap in the closed position. Various arrangements are known for forming the upper and lower panels sealed about the three sides, including folding the envelope blank approximately in half and sealing along the remaining two of the three sides, or alternatively folding side flaps and an end flap inwardly and sealing along the lower side and center seam.
While the folding and sealing of such envelopes may be readily accomplished with prior art devices, these devices have typically had difficulty attaching the clasp to the envelope. This is due to the fact that the clasp is typically attached to the envelope by passing one or more prongs struck from the clasp through the back panel of the envelope and then deforming these prongs to fix the clasp in place.
This arrangement is preferable in that it provides a strong attachment with low material costs, but it has been difficult to avoid damaging the front panel during the attachment step. This attachment step has often been carried out on a separate machine from that which folds and seals the envelope, resulting in increased complexity and capital outlays.
Another problem in the prior art has been the formation of apertured clasp envelopes. Such envelopes are similar to those described above, but include a series of apertures extending through the pouch portion of the front and back panels. These apertures allow viewing to determine if contents are present within the envelope, and are typically employed for interoffice mail.
On difficulty experienced in the prior art method and devices has been in the registration of these apertures. In particular, the location of the apertures in the envelope blank, and the location of the fold or folds to form the front and back panels, must be tightly controlled to ensure that the apertures are properly registered. This tight control has required prior art assembly machines to be more expensive and require constant adjustment. A second difficulty is that perforating to form the apertures takes place prior to folding, and the chips formed by perforation tend to either back up in the dies or become strewn downstream, interfering with other operations in the envelope forming process.
One prior art device for producing such envelopes is available from the W & D Machinery Company, Inc. of Overland Park, Kans., under model Helios 249. In this device, a roll of stock paper is mounted at the input end and fed into the device. The stock paper passes over appropriate tensioners, and printing means if applicable. Thereafter, the paper undergoes one or more appropriate cutting and scoring steps to remove material to form a continuous series of unfolded envelope blanks. Appropriate adhesive is applied to those flaps which will form the back panel of the envelope, and these flaps are then folded by appropriate guides.
During this folding, the flaps to form the back panel are folded over a support plate which is thus received between the front and back panels of the partially formed envelope. Once the flaps to form the back panel have been properly folded down, a clasp attaching device as shown in U.S. Pat. No. 4,994,010 forces the prongs of the clasp into the back panel of the envelope using the support plate as an anvil. Thereafter, a set of pinch rollers complete the deformation of the prongs, again using the support plate as an anvil.
Following attachment of the clasp, the continuous strip of partially formed envelopes are severed to form individual partially formed envelopes, and adhesive is applied to the lower flap which is then folded into position. If appropriate, an adhesive for later sealing of the top flap is applied thereto and the envelopes placed in a partially overlapping relationship ("collated") with the top flaps being exposed. These collated envelopes are then fed through a dryer to remove all tackiness from the adhesive applied to the top flap. Thereafter, the envelopes are removed from the collated relation, the top flap folded to its closed position, and the envelopes formed into a stack.
While the Helios 249 device has greatly improved the ease of attaching the clasp to the back panel, it still suffers from the above-noted problems of registration of the apertures in the front and back panels and chip distribution. Additionally, the clasp attaching mechanism is adjustable vertically as a whole with respect to the guide bar/anvil, which requires a great deal of trouble to adjust the insertion of the clasp prongs.